1. Technical Field
This application relates to a vascular device and more particularly to a vascular device for approximating the vessel wall and placing a valve for treating venous valve insufficiency.
2. Background of Related Art
Veins in the body transport blood to the heart and arteries carry blood away from the heart. The veins have one-way valve structures in the form of leaflets disposed annularly along the inside wall of the vein which open to permit blood flow toward the heart and close to prevent back flow. That is, when blood flows through the vein, the pressure forces the valve leaflets apart as they flex in the direction of blood flow and move towards the inside wall of the vessel, creating an opening therebetween for blood flow. The leaflets, however, do not normally bend in the opposite direction and therefore return to a closed position to prevent blood flow in the opposite, i.e. retrograde, direction after the pressure is relieved. The leaflet structures, when functioning properly, extend radially inwardly toward one another such that the tips contact each other to block backflow of blood.
In the condition of venous valve insufficiency, the valve leaflets do not function properly as they thicken and lose flexibility, resulting in their inability to extend sufficiently radially inwardly to enable their tips to come into sufficient contact with each other to prevent retrograde blood flow. The retrograde blood flow causes the buildup of hydrostatic pressure on the residual valves and the weight of the blood dilates the wall of the vessel. Such retrograde blood flow, commonly referred to as reflux, leads to swelling and varicose veins, causing great discomfort and pain to the patient. Such retrograde blood flow, if left untreated can also cause venous stasis ulcers of the skin and subcutaneous tissue. There are generally two types of venous valve insufficiency: primary and secondary. Primary venous valve insufficiency is typically a condition from birth, where the vein is simply too large in relation to the leaflets so that the leaflets cannot come into adequate contact to prevent backflow. More common is secondary venous valve insufficiency which is caused by clots which gel and scar, thereby changing the configuration of the leaflets, i.e. thickening the leaflets creating a xe2x80x9cstub-likexe2x80x9d configuration. Venous valve insufficiency can occur in the superficial venous system, such as the saphenous veins in the leg, or in the deep venous system, such as the femoral and popliteal veins extending along the back of the knee to the groin.
A common method of treatment of venous valve insufficiency is placement of an elastic stocking around the patient""s leg to apply external pressure to the vein, forcing the walls radially inwardly to force the leaflets into apposition. Although sometimes successful, the tight stocking is quite uncomfortable, especially in warm weather, as the stocking must be constantly worn to keep the leaflets in apposition. The elastic stocking also affects the patient""s physical appearance, thereby potentially having an adverse psychological affect. This physical and/or psychological discomfort sometimes results in the patient remove the stocking, thereby preventing adequate treatment.
Another method of treatment has been developed to avoid the discomfort of the stocking. This method involves major surgery requiring the implantation of a cuff internally of the body, directly around the vein. This surgery requires a large incision, resulting in a long patient recovery time, scarring and carries the risks, e.g. anesthesia, inherent with surgery.
Another invasive method of surgery involves selective repairing of the valve leaflets, referred to as valvuloplasty. In one method, sutures are utilized to bring the free edges of the valve cusp into contact. This procedure is complicated and has the same disadvantages of the major surgery described above.
Co-pending, commonly assigned U.S. patent application Ser. Nos. 09/877,639 and 09/877,480, incorporated herein by reference, disclose an advantageous method and device to minimally invasively treat venous valve insufficiency without requiring an outer stocking or internal cuff. Such device avoids the physical and psychological discomfort of an external stocking as well as avoids the risk, complexity and expense of surgically implanted cuffs. The device is advantageously inserted minimally invasively, i.e. intravascularly, and functions to effectively bring the valve leaflets into apposition. This device first expands against the vessel wall to grasp the wall, and then contracts to bring the vessel wall radially inwardly so the leaflets can be pulled closer together to a functional position. The present application utilizes the device of these prior applications for bringing the vessel wall radially inwardly to correct the dilation of the wall, but rather than rely on the patient""s existing valve leaflets which may be scarred or non-functional, contains a replacement valve as a substitute for the patient""s leaflets. Thus, advantageously, venous valve insufficiency can be treated minimally invasively by bringing the vessel wall inwardly and replacing the patient""s valve.
The present invention provides a vascular device comprising a plurality of vessel engaging members and a valve. The device is movable from a collapsed insertion position having a first diameter to a second expanded position having a second diameter larger than the first diameter. The plurality of vessel engaging members extend outwardly from the device for securely engaging the internal wall of a vessel upon expansion of the device to the second expanded position, wherein the vessel engaging members pull the internal wall of the vessel radially inwardly upon movement of the device from the second expanded position toward a first expanded position having a third diameter. This third diameter is greater than the first diameter and less than the second diameter. In the first expanded position the valve is movable between an open position to allow blood flow therethrough to a closed position to prevent blood flow.
The device is preferably composed of shape memory material and preferably the first expanded position substantially corresponds to the memorized position of the device. The device is expanded to the second expanded position by an expandable device, such as a balloon, positioned within the device.
In one embodiment, the device is initially movable from the collapsed position to the first expanded position in response to exposure to body temperature, and is subsequently moved from the first expanded position to the second expanded position by an expandable member. In another embodiment, the device is movable from the collapsed position to the second expanded position by the substantial simultaneous exposure to body temperature and expansion by an expandable member.
The present invention also provides a vascular system comprising a balloon catheter having an elongated shaft and an expandable balloon, a vascular device mounted over the expandable balloon and having a first position and a second expanded position, and a valve connected to the vascular device and movable between a closed position to prevent blood flow and an open position to allow blood flow therethrough. The vascular device is expandable to the expanded position to engage the vessel walls and returnable substantially to the first position to bring the walls radially inwardly.
The vascular device in one embodiment comprises a shape memory material and can be expandable first to a memorized condition in response to exposure to body temperature and subsequently expanded to the expanded position by inflation of the balloon. Alternatively, the vascular device can be expandable to the expanded position as the device is substantially simultaneously exposed to body temperature and the balloon is inflated. The device in another embodiment can be composed of stainless steel and is expandable by the balloon below its elastic limit to enable return of the device to the first position.
In the foregoing devices and system, the vascular device can be releasably connected to the balloon. The valve can be attached to a distal end of the vascular device to extend downstream of the device when positioned within a patient. Alternatively, the valve can be attached to a proximal end of the vascular device to extend within a central portion of the device when positioned within a patient. The valve is preferably substantially conical in shape. The valve can alternatively have a duckbill valve configuration. In one embodiment, a longitudinal axis of the valve is offset from a longitudinal axis of the vascular device. The valve may include a plurality of blood drainage openings extending through a side wall. A reinforcement ring can be provided adjacent the distal opening.
The present invention also provides a method for treating venous valve insufficiency comprising:
inserting a delivery device and a vascular device having a replacement valve into a target vessel adjacent the region of the removed portion of leaflets;
deploying the vascular device to an enlarged diameter to securely engage the internal wall of the vessel; and
reducing the diameter of the vascular device to move the vessel wall radially inwardly to reduce dilation of the vessel and implant the replacement valve.
The method can further include the step of removing at least a portion of vein valve leaflets of a patient before inserting the vascular device.
In one embodiment, the method further comprises the step of deploying the vascular device to a first expanded diameter prior to deploying the device to the enlarged diameter, the first expanded diameter being less than the enlarged diameter, and the step of reducing the diameter of the vascular device returns the device to a diameter substantially equal to the first expanded diameter. In this embodiment, the step of deploying the vascular device to a first diameter preferably comprises the step of exposing the vascular device from a sheath of the delivery device to enable the vascular device to return a shape memorized configuration in response to being warmed by body temperature. The step of the deploying the vascular device to an enlarged diameter in this embodiment preferably includes the step of inflating a balloon positioned within the device.
Alternatively the step of deploying the vascular device to an enlarged diameter comprises releasing the vascular device from the delivery device to enable it to return to a shape memorized condition and substantially simultaneously inflating a balloon.
The delivery device can be inserted through the jugular vein or femoral vein into the popliteal vein or the saphenous vein.
In another aspect, the present invention provides a replacement valve comprising a support structure and a valve attached thereto, the valve being substantially conical in configuration and having a distal opening facing away from the longitudinal axis when the valve is in the closed position and aligned with the longitudinal axis when the valve is in the open position.
In one embodiment the valve is attached to a proximal end of the support structure, and in another embodiment the valve is attached to a distal end of the support structure. In one embodiment, the valve is offset with respect to the longitudinal axis of the support structure. The valve can optionally include a plurality of drainage openings formed in a side wall adjacent the proximal end.